The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in the present disclosure and are not admitted to be prior art by inclusion in this section.
In some networks, observed time difference of arrival (OTDOA) may be used to locate the physical position of a user equipment (UE). Specifically, a reference signal (RS) such as a positioning reference signal (PRS) may be transmitted from multiple transmit stations (sometimes also referred to as transmit points (TPs)), and the UE may measure a reference signal time difference (RSTD) for each received RS. The transmit stations may be, for example, access points, evolved NodeBs (eNBs), remote radio heads (RRHs), or some other type of base station for a network (collectively referred to herein as “transmit stations”).
In some cases, the transmit stations may be transmit stations of a coordinated multiple point (CoMP) network scenario-4. In those cases, the transmit stations may have identical physical cell identifiers (PCIDs). In such a scenario, the RS sequence or resource element (RE) allocation of the RSs of each transmit station may be identical because the RS sequence and RE mapping may be initialized by the identical PCIDs, which may result in identical RSs. Additionally, the REs on which the RSs are transmitted may be identical because the resource element allocation may also be based on the identical PCIDs. Because the transmitted RSs from the multiple transmit stations are identical, and transmitted on identical REs, the received signal at the UE may appear as single frequency network (SFN) combined waveforms which may be indistinguishable from one another. Therefore, the UE may not be able to measure RSTD for each cell.
Similarly, primary synchronization signals (PSSs), secondary synchronization signals (SSSs), cell specific reference signals (CRSs), and channel state information reference signals (CSI-RSs) (collectively referred to herein as discovery reference signals (DRSs)) from the different TPs may also be indistinguishable from one another because the DRSs may also be based on the identical PCID used by each transmit station. As used herein, the various reference signals such as PRS, PSS, SSS, CRS, CSI-RS, DRS, etc., will be generically referred to as “RSs.”